Separation of metallic from nonmetallic particles



Sept. 21, 1954 T. E. MAESTAS SEPARATION OF METALLIC FROM NONMETALLIC PARTICLES Filed Feb. 18, 1952 4 m I. n m 2 a 3 u Roy. H :2 F M a w w SJ W D 1 I 3 a i l h w h s a u w. m IN. 7 O a 2 w w. r l a I. u a m w 9 h 0 I!- I. 2 1 H O I o :5: ii Fl? o M O Snuentor E. MAESTAS FWHITEHEAD VOGL W PER {alt/Q (Ittomeg THOMAS Fig. 3

Patented Sept. 21,1954

SEPARATION OF METALLIC FROM NONMETALLIC PARTICLES Thomas E. Maestas, Boise, Idaho, assignor of one-half to Doenges-Long Motors, Inc., 0010- rado Springs, 0010., a corporation of Colorado Application February 18, 1952, Serial No. 272,115

' Claims. 1

This invention relates to the segregation and concentration of the metallic constituents within a body of comminuted particles through means which utilize the ability of the bulk of the nonmetallic particles to become electrostatically charged and react to forces created in an electrostatic field. More specifically, the invention relates to means for the segregation and concentration by stratification of metallic particles which do not respond to electrostatic charges from non-metallic particles which do so respond, followed by a mechanical separation of the resultant layers of the two types of particles. For purposes of this application the two types of particles will be referred to as metallic and nonmetallic particles, although it is to be understood that the invention functions because of the basis characteristic of some types of particles to hold and respond to an electrostatic charge and other types of particles, generally metallic particles, not to hold an electrostatic charge.

- The objects of the invention include the provision of a new and improved apparatus wherein: (1) there is continuous segregation of metallic and non-metallic particles into strata as the particles pass through an alternating electrostatic field; (2) by such segregation, it is possible to divide out the bulk of the non-metallic particles to obtain a body of particles having a high proportion of metallic particles; (3) such division out or separation of the metallic and non-metallic particles after they are segregated into strata is accomplished in an extremely simple manner; (4) means are provided for regulating the intensity of the electrostatic field along the path of the movement of the particles; (5) segregation is possibleregardless of the density and size of the particles; (6) it is possible to process a continuous flow of comminuted material; ('7) the arrangement of elements to accomplish the aforestated objects provides an apparatus which is extremely simple in construction, economical to operate and adapted for use with a variety of materials.

With these and other objects in view, all of which more fully hereinafter appear, my invention comprises certain novel constructions, combinations and arrangements of elements and parts as herein described, and as defined in the appended claims, and illustrated, in preferred embodiment, in the accompanying drawing, in which:

Figure 1 is a plan view of the apparatus.

Figure 2 is an elevation view partly in section as taken substantially on the indicated line 2-2 at Fig. 1.

Figure 3 is a transverse sectional view as taken on the indicated line 3-3 at Fig. 2.

Figure 4 is a fragmentary section of elements shown at Fig. 2, but taken on a considerably enlarged scale.

The art of concentrating the mineral constituents of a body of comminuted material through Stratification has generally relied upon the differences between the density of the various components in the body, and the means for effectuating the stratification has generally been some form of vibratory apparatus. However, separation and stratification by vibration has never been satisfactory, because vibration results in stratification as between particles of the same substance but of different sizes and the particle size of the components of the body must be practicaliy uniform before efficient separation of the different kinds of components is possible. Actually, itis practically impossible to separate the material where there is large variation in particle sizes. Nevertheless, the process of obtaining concentrates by separation, into strata, of the desirable mineral constituents from the waste materials, has appealed to the mining profession, and considerable experimentation has been made along such lines. r

The present invention has departed from the most obvious method of stratification, namely by vibration, and relies upon the fact that different types of particles, such as metallic and nonmetallic particles; will react differently when placed in an electrostatic field of alternating potential. The metallic particles will remain at rest and the non-metallic particles will vibrate. More specifically, non-metallic particles, such as sand, are non-conductors, andpossess dielectric propertieswhich permit them to become electrostatically charged and attracted to or repelled from an electrode, while metallic particles, such as gold, which may be intermixed with the sand particles, are generally conductors which have no dielectric properties and cannot become charged or attracted to an electrode. Thus the movement of a body of comminuted particles into a field of alternating potential results in an irregular oscillatory movement of the non-metallic particles, leaving the metallic particles quiescent, the natural result being that the metallic particles will settle to form a layer below the body of turbulent non-metallic particles. With this result in view, the present invention was conceived and developed, and comprises apparatus which provides means for passing a continuous flow of comminuted particles through an alternating electrostatic field to effect a stratification of the 3 constituent particles, combined with means for physically separating the stratified layers as they leave the electrostatic field.

In preferred embodiment, the apparatus is mounted upon a framework including suitable posts It; and Illa. and struts and beams arranged to carry the operative elements in which the invention is embodied and which include a conveyor element which is an endless belt I I made of rubber, rubber fabric, or any similar material having,

among other characteristics, a high dielectric strength. This belt extends the length of the machine and travels around a pair of shafted roll.- ers l2 and I211. The shafts, l3 and [3a respectively, are journaled respectively at the opposite ends of the frame and are horizontally disposedin spaced parallelism whereby the upper belt reach, spanning the gap between the rollers, forms a. surface which lies in a horizontal plane. It follows that rotation of the rollers and movement of belts provides a flat surface whereon comminuted material may be continually carried lengthwise across the machine.

The shaft I30. extends laterally through a journailing frame member to provide a stub whereon is mounted a pulley 14 which is connected to a pulley l of a drive motor It by a belt II. The motor and pulleys are adapted to drive the belt I I at a selected uniform rate, and for changing the belt speed to any optimum rate the motor is equippedwith aconventionalspeed regulator element l8. As. shown by the indicated arrow; the movement of the upper reach of the belt is from the roller [2 toward the roller [200. Any other mechanism for moving the belt in said manner and rate may be used.

In operation of the apparatus it is. desirable to flow the comminuted material, hereinafter referred to as sand, onto the belt H at a uniform rate, and to spread the material evenly upon the upper belt surface so that as the belt moves it will carry a continuous layer of uniform thickness. The sand may be supplied to the ap aratus through discharge from a conventional 1101 1 61 19 which may be mounted upon frame-members Illa above the belt. The base of the hopper is elongated transversely to accommodate a. transverse cylinder valve 20, or other conventional valve, which functions to regulate the flow ofsand. from the hopper. It is. desirable that. the valve, orifice 21, be elongated transversely to provide an. initial material spread. The flow of sand fromhthe hop: per is controlled by rotation of the valve as by a. handle. 22.

The, sand drops upon. a spreader pan 23,. which provided. with .a vibrator 2.4 whichvibrates the pan and thereby deposits upon the belt H in a layer .of uniform thickness, the sand from. the pan.

The. upper belt reach is enclosed. by baflle boards 25 along and against. eachside edge of the belt to form a channel and thereby confine the sand to-the'belt. The baflie boards 25 extend beyond the roller 1200, which is the discharge end of the belt, tomerge with collector chutes, all as hereinafter described.

A pair of rectangular-electrode plates 26 and 26a are placed respectively above and below the upper belt reach to provide anelectrostatic field through which the loaded upper reach of the belt passes. These plates are rectangular, and so proportioned as to extend over a substantial length and width of. the belt upper reach. Assuch electrodeplates are subjected to high voltage they are mounted upon insulating brackets 21 The insulating brackets 21 at the lower electrode 26 are attached to cross struts of the frame to hold the electrode 26 against or in close proximity to the under side of the upper belt reach and in parallelism therewith, as indicated in the drawing.

The; insulating brackets 21 which .carry the upper electrode plate 2.6a are attached to lift screws 28 which upstand from brackets 21 to extend through frame cross struts and are threaded into worm gears 29, whereby rotation of the gears raises or lowers-the electrode 26a. The worms of the gears 29 are carried on a common shaft 36 which may be rotated by a handle 3|. It is anticipated that the upper electrode 2621 will be normally in spaced parallelism with the upper belt reach and adjustable to any desired space therebetween. Further adjustment, whereby the electrode may be tilted in the direction of the belt movement, to provide a converging or diverging electrostatic field, is possible ,by ,means. of anadjusting screw v32 between the bracket 2] and lift screw 28. This. adjusting screw may have a knurled surface for easy manipulation.

The power to create an electrostatic field be,- tweenithe plates. 2 6. and 26a issupplied byan alternating current source, as through a power supply line 33 of a desirable frequency. This supply line 33 is connected to a step-up transformer 34 to obtain a desired voltage. The terminals of the step-up transformer are in turn connected with the electrodes 26 and 26a through leads 35 and 35a respectively.

The movement of the sand through the. electrostatic field causes the non-metallic sand par.-

ticles to become charged and. physically vibrate within the field, and by virtue of such movement, the charged particles are lifted and the metallic or uncharged particles M are sifted downward to lie against the belt surface H as clearly shown at Fig. 4. The belt movement through the field is so timedthat this sifting and stratifying of the sand particles is completed by the time the particles emerge from the field between the electrodes. The necessary adjustments and timing for a given type of sand is possible by experimentation.

Upon moving from the electrodes, thestratified particles are carried over the roller iZa tofall into the collector chutes at the end of the apparatus. Two collector chutes are provided, an innerchute 36' and an outer chute 31 each of belt width, with the side baifles 2 5 merging into wall elements defiling the chutes. The chutes are adapted .to convey or retain material inany" conventional manner, and therefore the details of their construction is not herein disclosed. Above the chutes and adjacent the roller 12a thereis atransverse dividing fin 38, which is swingin-gly mounted upon a shaft 39' and adjusted by turning a handle 40' topermit its leading edge to be set at any given distance from the upper belt surface as it passes over roller I211 and to thereby bifurcate the. flow of Stratified sand at any desirable depth.

It follows that in the operation of this machine, the separation of particles by the fin 38 may be such that the concentration of metallicmaterials also includes a substantial portion of non-metallic material, especially where only small amounts of metallic materials, as gold, are present. To,pro,- vide for such, cases, any suitable arrangement may be made, for moving. the concentrated sand from chute. 35, back into. the hopper 1.9;, for fur. ther separation by repetition of the above: dc.-

scribed treatment in order to obtain a higher concentration.

While I have described in detail a preferred embodiment of my invention, alternatives and equivalents of construction which are within the scope and spirit of my invention will occur to those skilled in the art, hence it is my desire that my protection be limited not by the details of arrangements and constructions herein illustrated and described, but only by the proper scope of the appended claims.

I claim:

1. The method of treating a mass of commingled metallic and non-metallic particles for concentration of the metallic particles comprising the moving of the mass upon a carrier having high dielectric strength through an electrostatic field of alternating potential for a substantial distance whereby to cause stratification of the particles with the metallic particles disposed below the non-metallic particles, and the separation of the stratified layers of particles.

2. A machine for the separations concentration of metallic particles which are commingled with a mass of non-metallic particles including, in combination, a conveyor having high dielectric strength adapted to carry the commingled particles along a substantially horizontal plane throughout a substantial reach, means to load the conveyor with a substantially uniform layer of the commingled particles, means for providing an electrostatic field of alternating potential across the conveyor throughout said reach, means for moving the loaded conveyor through said field, said potential being sufficient to cause continued vibration of the non-metallic particles whereby the metallic particles are sifted through the layer to a position underlying the non-metallic particles, and means beyond the field for dividing the layer.

3. A machine for separating metallic particles from a mass in which they are commingled with non-metallic particles, including, in combination, a conveyor belt of dielectric material whose upper reach is flat and lies in a substantially horizontal plane throughout a substantial length, means for depositing commingled particles in a uniform layer upon the belt at one end of said flat reach, electrodes beneath and above said. belt reach comprising fiat plates as wide as said belt and extending through said reach, means for charging the electrodes with alternating potential to create an electrostatic field coextensive with said reach, means for moving said belt, whereby the carried particles are continuously moving through said field whereby to vibrate the non-metallic particles and cause the metallic particles to be sifted to a layer adjacent the belt surface, and means, associated with the belt, to separate the layer of metallic particles lying upon the belt from the non-metallic particles above.

4. The machine defined in claim 3 wherein the lower electrode plate lies closely adjacent to the said belt reach and said upper electrode lies above and normally in substantially spaced parallelism with said belt-reach.

5. The apparatus defined in claim 4 wherein said upper electrode plate is provided with means for varying the spacing of said upper electrode plate from the belt and for including the plate relative to said upper belt-reach.

References Cited in the file of this patent UNITED STATES PA'IEN'IS Number Name Date 1,110,896 Comstock Sept. 15, 1914 1,218,916 Weatherly Mar. 13, 1917 1,386,287 Sutton Aug. 2, 1921 2,470,889 Drescher May 24, 1949 

